Mate location by diaptomid copepods

Female diaptamid copepods oscillate frequently between gravidand non-gravid conditions (about every 4 days at 18°C, inthose species tested). Since viable egg sacs have been producedonly by females mated during the gravid phase of this cycleand since remating is required for each clutch, experimentswere conducted to determine whether mate selection was relatedto the reproductive condition of females, thus maximizing reproductiveeffort. The results indicated that males pursue and attemptto mate with any congener approached caudally, apparently usinga hydrodynamic signal in the swimming wake as an initial cue,but they are most successful in catching gravid females. Theseresults suggest the existence of a discriminatory mechanismwhich is linked to the female's reproductive cycle. The purportedmechanism operates after a potential mate is initially perceived,and it may involve a modification of the female's escape behavioror the production of a pheromone. Further attempts to definethe mechanism should concentrate on differences between gravidand non-gravid females. ¹Present address: R.M. Parsons Laboratory, 48-429, MassachusettsInstitute of Technology, Cambridge, MA 02139, USA.